方法调用中的静态变量空,但在程序中初始化

Question

我在这里有点头疼,我想知道是否有人知道答案.

设置基本上是这样的:

//in Visual Studio plug-in application
SpinUpProgramWithDebuggerAttached();

//in spun up program
void Start()
{
    StaticClass.StaticVariable = "I want to use this.";
    XmlSerializer.Deserialize(typeof(MyThingie), "xml");
}

class MyThingie : IXmlSerializable
{
     ReadXml()
     {
         //why the heck is this null?!?
         var thingIWantToUse = StaticClass.StaticVariable;
     }
}

让我脱头发的问题是,在IXmlSerializable.ReadXml()方法中,StaticClass.StaticVariable为null,即使在设置变量后它被称为RIGHT.

值得注意的是,没有命中断点,并且在问题发生的精确位置忽略Debugger.Launch().

神秘的是,我通过提出异常来确定AppDomain.CurrentDomain.FriendlyName属性对于静态变量填充的位置与null相同!

为什么heck是超出范围的静态变量？!？这是怎么回事？!？我如何分享我的变量？

编辑:

我根据响应中的建议添加了一个静态构造函数,并让它执行Debug.WriteLine.我注意到它被调用了两次,即使所有代码似乎都在同一个AppDomain中运行.这是我在输出窗口中看到的内容,我希望这是一个有用的线索:

静态构造函数调用时间:2015-01-26T13:18:03.2852782-07:00

...加载'C:...\GAC_MSIL\System.Numerics\v4.0_4.0.0.0__b77a5c561934e089\System.Numerics.dll'...

......加载'Microsoft.GeneratedCode'......

...加载'C:...\GAC_MSIL\System.Xml.Linq\v4.0_4.0.0.0__b77a5c561934e089\System.Xml.Linq.dll'....

...加载'C:\ USERS ...\APPDATA\LOCAL\MICROSOFT\VISUALSTUDIO\12.0EXP\EXTENSIONS ... SharePointAdapter.dll'.符号已加载.

...加载'Microsoft.GeneratedCode'.

静态构造函数调用时间:2015-01-26T13:18:03.5196524-07:00

附加细节:

这是实际的代码,因为有几位评论者认为它可能有所帮助:

//this starts a process called "Emulator.exe"
var testDebugInfo = new VsDebugTargetInfo4
{
    fSendToOutputWindow = 1,
    dlo = (uint)DEBUG_LAUNCH_OPERATION.DLO_CreateProcess,
    bstrArg = "\"" + paramPath + "\"",
    bstrExe = EmulatorPath, 
    LaunchFlags = grfLaunch | (uint)__VSDBGLAUNCHFLAGS.DBGLAUNCH_StopDebuggingOnEnd | (uint)__VSDBGLAUNCHFLAGS.DBGLAUNCH_WaitForAttachComplete,
    dwDebugEngineCount = 0,
    guidLaunchDebugEngine = VSConstants.CLSID_ComPlusOnlyDebugEngine,
};

var debugger = Project.GetService(typeof(SVsShellDebugger)) as IVsDebugger4;
var targets = new[] { testDebugInfo };
var processInfos = new[] { new VsDebugTargetProcessInfo() };

debugger.LaunchDebugTargets4(1, targets, processInfos);

//this is in the emulator program that spins up
public partial class App : Application
{
    //***NOTE***: static constructors added to static classes.
    //Problem still occurs and output is as follows (with some load messages in between):
    //
    //MefInitializer static constructor called at: 2015-01-26T15:34:19.8696427-07:00
    //ContainerSingleton static constructor called at: 2015-01-26T15:34:21.0609845-07:00. Type: SystemTypes.ContainerSingleton, SystemTypes, Version=1.0.0.0, Culture=neutral, PublicKeyToken=...
    //ContainerSingleton static constructor called at: 2015-01-26T15:34:21.3399330-07:00. Type: SystemTypes.ContainerSingleton, SystemTypes, Version=1.0.0.0, Culture=neutral, PublicKeyToken=...

    protected override void OnStartup(StartupEventArgs e)
    {
         //...

         //initializes a MEF container singleton (stored as static variable)
         MefInitilizer.Run(); 

         //here's where it blows up. the important details are that 
         //FullSelection implements IXmlSerializable, and its implemention
         //ends up referencing the MEF container singleton, which ends up
         //null, even though it was initialized in the previous line.
         //NOTE: the approach works perfectly under a different context
         //so the problem is not the code itself, per se, but a problem
         //with the code in the environment it's running in.
         var systems = XmlSerialization.FromXml<List<FullSelection>>(systemsXml);
    }
 }

public static class MefInitilizer
{
    static MefInitilizer() { Debug.WriteLine("MefInitializer static constructor called at: " + DateTime.Now.ToString("o")); }

    public static void Run()
    {
        var catalog = new AggregateCatalog();
        //this directory should have all the defaults
        var dirCatalog = new DirectoryCatalog(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location));
        //add system type plug-ins, too
        catalog.Catalogs.Add(dirCatalog);

        var container = new CompositionContainer(catalog);
        ContainerSingleton.Initialize(container);
    }
}

public class ContainerSingleton
{
    static ContainerSingleton() 
    {
        Debug.WriteLine("ContainerSingleton static constructor called at: " + DateTime.Now.ToString("o") + ". Type: " + typeof(ContainerSingleton).AssemblyQualifiedName);
    }
    private static CompositionContainer compositionContainer;

    public static CompositionContainer ContainerInstance
    {
        get 
        {
            if (compositionContainer == null)
            {
                var appDomainName = AppDomain.CurrentDomain.FriendlyName;
                throw new Exception("Composition container is null and must be initialized through the ContainerSingleton.Initialize()" + appDomainName);
            }
            return compositionContainer; 
        }
    }

    public static void Initialize(CompositionContainer container)
    {
        compositionContainer = container;
    }
}

Answer 1

感谢所有提出建议的人！我从来没有弄清楚到底发生了什么（如果我这样做的话，我会继续调查/发布更新），但我最终确实想出了一个解决方法。

一些人建议将静态类的初始化内部化，但由于实际问题的性质，初始化逻辑必须外部化（我基本上是加载一个 DI/服务位置容器，其组成因环境而异）。

另外，我怀疑它不会有帮助，因为我可以观察到静态构造函数被调用了两次（因此，无论有什么初始化逻辑都只会被调用两次，这并没有直接解决问题）。

然而，这个建议让我走上了正轨。

就我而言，我加载的服务都不需要是有状态的，因此除了性能影响之外，初始化发生两次并不重要。

因此，我只是让静态类检查 MEF 容器是否已加载，如果没有加载，我将读取指定处理初始化的类的配置文件。

通过这样做，我仍然可以根据环境改变 MEF 容器的组成，目前它运行得很好，即使它不是理想的解决方案。

我想在所有提供帮助的人之间分配赏金，但由于这似乎不可能，我可能会奖励 OakNinja，因为他是一位英雄，根据我提供的信息，提出了尽可能多的好主意。假如。再次感谢！